Kosterlitz-Thouless Transition of Quantum XY Model in Two Dimensions

Abstract

The two-dimensional S=1/2 XY model is investigated with an extensive quantum Monte Carlo simulation. The helicity modulus is precisely estimated through a continuous-time loop algorithm for systems up to 128 × 128 near and below the critical temperature. The critical temperature is estimated as T_KT = 0.3427(2)J. The obtained estimates for the helicity modulus are well fitted by a scaling form derived from the Kosterlitz renormalization group equation. The validity of the Kosterlitz-Thouless theory for this model is confirmed.